Beta-cyclohomocitral is a valuable substance useful in the formulation of perfumery, tobacco and food flavoring materials, as disclosed in copending Application for U.S. Letters Pat. No. 507,412 filed on Sept. 19, 1974.
The preparation of beta-cyclohomocitral and beta-ionone enol acetate (an intermediate for producing beta-cyclohomocitral is set forth in British Patent 775,060, which discloses (A) first forming an "iso-C.sub.11 -aldehyde" by (i) condensing ethoxy-acetylene with 2,6,6-trimethylcyclohexanone-1, (ii) partially hydrogenating the resulting acetylenic carbinol so as to convert the triple bond therein into a double bond, and (iii) treating the resuling olefinic compound with an acid; then (B) reacting the resulting iso-C.sub.11 -aldehyde with acetic anhydride and fused sodium acetate under reflux conditions to form beta-ionone enol acetate; and (C) hydrolyzing the beta-ionone enol acetate with alcoholic base (sodium bicarbonate-methanol mixture) to form beta-cyclohomocitral. This multi-step sequence of reactions and the low yield of final product render the synthesis of British Patent No. 775,060 commercially impractical.
Reactions of peracetic acid with .alpha.-aralkylidenecyclanones in the presence of buffer are disclosed by Walton J. Org. Chem., 22, 1161 (1957), for example: ##SPC4##
Wherein R is phenyl, substituted phenyl or 2-furyl and n is 3 or 4.
Broadly, the reaction of a system containing conjugated unsaturation with a peroxidation agent is known (See Wenkert and Rubin, Nature 170, 708 (1952) wherein the reaction of an alpha, beta-unsaturated ketone having a phenyl moiety in the beta position is oxidized to form an enol ester is taught) but reaction of an ionone type material with an oxidizing agent to form an acyloxyethylene moiety (as opposed to an epoxide moiety) has been heretofore unknown. Also see Boesken et al., Rec. Trav. Chim. 50, 827 (1931); 52,874 (1933); 55,786 (1936), who have shown that peroxyacetic acid reacts with benzalacetone and related ketones with the insertion of an oxygen atom between the carbonyl and styryl groups, resulting in the formation of enol esters of phenylacetaldehyde and benzyl ketones. A relevant reaction taught by Boeseken et al. is as follows: ##SPC5##
wherein R.sub.1 and R.sub.2 are each hydrogen or methyl.
FMC Corporation "Preparation, Properties, Reactions and Uses of Organic Peracids and Their Salts" discloses methods for the preparation of peracetic acid, performic acid and perpropionic acid at pages 3-21 and discusses the use of peracids in carrying out Baeyer-villiger oxidations of unsaturated ketones at pages 84-89.